The present invention relates in general to 1) navigation technology used to aid SCUBA divers in navigating while diving and 2) SCUBA diving flags required by law when diving.
Safety is strongly influenced by the ability to navigate while underwater. Many divers become lost and/or disoriented while SCUBA diving every year. Some of those lost divers do not survive due to complications that arise as a result of becoming lost (e.g. running out of air). One of the most common dive scenarios is one where a diver enters the water from a boat with the intention of returning to the boat after the dive. Far too many times, divers surface far from the boat as a result of becoming completely lost while underwater. The resulting surface swim can be very strenuous causing a diver to become exhausted or possibly to have a heart attack, and require rescuing. SCUBA divers are taught basic navigation using a magnetic compass at multiple levels of course instruction from novice to advanced. The patterns taught to divers are very basic such as straight lines, and square boxes. Divers are not taught effective techniques to compensate for water currents, and are only taught very basic knowledge of how to maintain proper positioning of the compass in inertial space. Human beings are not very good navigation computers as they cannot repeatedly place a compass in precisely the same attitude, cannot compensate for hard and soft iron effects in their heads, cannot remember a multitude of turns (changing headings) nor easily calculate a return heading after an actual dive (other than straight out and back). The task of underwater navigation is further complicated by environmental factors such as visibility, lack of bottom features (e.g. barren sandy bottom) and/or water currents. Other factors that exacerbate underwater navigation by divers is loss of concentration/awareness due to excitement, task loading, photography or harvesting sealife (e.g. lobster, spearfishing etc.). Appreciation for the navigation problem for SCUBA divers has spawned a multitude of systems being designed. Most systems employ a system of acoustic transponders and/or beacons to communicate with a receiver held by a diver (U.S. Pat. No. 5,185,725 Kent et al, U.S. Pat. No. 5,570,323 Prichard et al, U.S. Pat. No. 5,241,516 Kruchowy et al, U.S. Pat. No. 5,148,412 Suggs). These systems, though adequate, are simply unaffordable to the common recreational or technical diver and are intended for use by mostly commercial and/or military divers. Additionally, a transponder-based system requires a network of transponders to provide navigation/location information to the diver. Such a transponder network is not easily retrieved and redeployed. Also, the divers simply deploying or retrieving the transponders could easily become lost themselves. A system that is self-contained and is not dependent upon local infrastructure is optimum. Self-contained navigation systems for SCUBA divers have been proposed. One system proposed by Wood, U.S. Pat. No. 5,747,700, employs the well-known combination of a flowmeter and a magnetic compass. However, Wood""s system, though self-contained, has a number of sources of error. The system proposed by Wood does not compensate for water currents. For example, a diver may be swimming north at 50 feet/second (fps) which Wood""s flowmeter may correctly register. However, if the diver is crabbing east at 20 fps, Wood""s design will not detect the cross current. Additionally, Wood uses a single compass, and a single flowmeter. With exception of regions over the magnetic poles and the equator, the earth""s magnetic field has both a vertical and a horizontal component. Unless at least two orthogonally mounted sensors are used, (or the divers precise attitude in inertial space, e.g. pitch and roll angles is known) a divers varying attitude will cause a single compass to read portions of both components, and thus provide incorrect heading information. Additionally, Wood""s system does not compensate for hard and/or soft iron effects on the magnetic compass that are normally present in a iron shipwreck, pipelines or underwater cables. In addition to the temporal nature of water currents, large objects such as shipwrecks distort water currents even further.
A system that is affordable, self contained, can compensate for water currents, and is not easily affected by large magnetic anomalies, and does not add additional infrastructure is needed. Preferably, the system would not require a diver to carry additional equipment so as not to further task load the diver.